Emergency treatment of severe hypertension with intravenous labetalol.

The effects of intravenously administered labetalol on blood pressure and pulse rate were examined in 17 patients with severe hypertension. Prompt and sustained falls in supine blood pressure and pulse rate occurred in ten patients (responders), but seven patients showed little or no change in either measurement (non-responders). Labetalol had a more marked effect on standing than on supine blood pressure. Only two of the responders, but all of the non-responders were concurrently receiving antihypertensive drugs. Plasma renin activity, plasma renin concentration and plasma angiotensin II concentration fell slightly over the one-hour period of observation in ten patients in whom serial measurements were made, but the changes were independent of the blood pressure response.